A compressor includes a casing and a rotor that rotates around an axis inside the casing. A rotor of an axial-flow compressor has a rotor shaft that extends around an axis in an axial direction, and a plurality of blade rows that are fixed to an outer circumference of the rotor shaft and arrayed in the axial direction.
Examples of such a rotor of an axial-flow compressor include the one disclosed in Japanese Patent Publication No. 2013-204593. In this rotor, a plurality of chambers (or cavities) are formed for the purpose of rotor weight reduction etc. Of the plurality of chambers, a first chamber and a second chamber are located side by side in the axial direction at the same position in the radial direction. The second chamber is located on the upstream side in the axial direction relative to the first chamber. Of the plurality of chambers, a third chamber is formed at a position between the first chamber and the second chamber in the axial direction, on the radially inner side of the first chamber and the second chamber. Both the first chamber and the second chamber communicate with an air compression flow passage that is formed by an annular space between the outer circumferential side of the rotor shaft and the inner circumferential side of the casing. The third chamber communicates with both the first chamber and the second chamber.
Part of air inside the air compression flow passage flows into the first chamber that is located on the downstream side of the second chamber. This air flows from the first chamber into the third chamber, and then returns into the air compression flow passage through the second chamber.